goodroi - 1:09 am on Jun 14, 2010 (gmt 0)
i would first change my sitemap from html to xml.
than i would make sure its not one of these three issues.
1) google glitch - google aint perfect and from time to time they will have a glitch that will fix itself.
2) invalid sitemap - check your sitemap with a online sitemap validator to make sure it is properly written. a single typo can cause havoc.
3) your site was/is down - if your hosting company isnt the most reliable it is possible for your website & sitemap to be unavailable when google tries to crawl it. simple solution is to make sure you have a good hosting company and use a site monitoring tool to ensure your site is always live.